Guo, F-J
Jiang, R
Xiong, Z
Xia, F
Li, M
Chen, L
Liu, C-J
Article History
Received: 23 January 2014
Revised: 27 March 2014
Accepted: 31 March 2014
First Online: 22 May 2014
Competing interests
: The authors declare no conflicts of interest.